The problem with Celestial Tower is that, 3F and above you also encounter Golbats, unlike BW1. So 2F is the only ideal spot for SpAtk training.

Castelia Sewers you have a 90% chance at a Zubat or Rattata, so adding. Other than Basculin farming this is probably the highest rate out there.

Victory Road is not ideal due to the high level (Celestial Tower is a better location due to Litwick being 20 levels lower) and due to the version exclusive.

Also any area where you have to fight Roggenrola or Boldore kind of suck. Roggenrola has Sturdy, Boldore has Sturdy and grants Attack EVs, which are undesirable if you only want Defense EVs. Unfortunately both BW1 and BW2 are plagued with poor areas to train in Defense.

I seem to be the only person who runs into grimers by walking.
Its really not surf only, they are just fairly rare (I used one though).
Anyway, nice guide. Especially since I am still doing the LC OIP for the week the EV training could really help since they kinda need the EVs. Could you maybe add a little more special attack though? There has got to be more than litwick worthy to put in the OP!

In a lot of cave parts (but not all), you only encounter Onix and Boldore, who give defense EVs.

In the outside parts, you encounter basculin and buizel by surfing, both give speed EVs.
By fishing in the cave you encounter basculin and poliwag (poliwhirl and poliwrath in bubling water), all of whom, excluding poliwrath, give speed EVs.

In the grove, you encounter roselia and petilil (cottonee in B2), who give special attack EVs.

In a lot of cave parts (but not all), you only encounter Onix and Boldore, who give defense EVs.

In the outside parts, you encounter basculin and buizel by surfing, both give speed EVs.
By fishing in the cave you encounter basculin and poliwag (poliwhirl and poliwrath in bubling water), all of whom, excluding poliwrath, give speed EVs.

In the grove, you encounter roselia and petilil (cottonee in B2), who give special attack EVs.

Click to expand...

Boldore gives +1 Atk in addition to +1 Def.

The other 2 are inferior to the other options, which have the same EVs and are lower in level too.